In a prior art method for controlling the fuel injection in an internal combustion engine, amount of fuel was increased when a signal representing the engine acceleration state, for example, the rate of change (.DELTA.Q/N) of the ratio (Q/N) between the intake air amount (Q) and the engine rotational speed (N), rose above a predetermined value. This increase was effected according to a fuel increase rate determined by a detected variable, such as the coolant water temperature. Increased fuel injection has been considered necessary, because engine acceleration, causes an increase in the intake air and hence, a temporary shortage of fuel supplied to the engine. This has a detrimental effect on the engine drivability.
The above prior art method, however, has the disadvantage in that when changing gears to shift speeds in a manual transmission automobile, an unnecessary increase of fuel takes place, causing the air-fuel ratio to become excessively rich and, hence, having detrimental effect on engine drivability.
This unnecessary increase of fuel takes place because the rate of change (.DELTA.Q/N) of the ratio (Q/N) changes during gear change in the same way as during engine acceleration. That is, there is no discrimination made between engine acceleration and a gear change operation.